1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor device of resin-encapsulation type using a rigid substrate.
2. Description of the Related Art
In a semiconductor device (semiconductor package) of surface mounting type, the semiconductor elements (chips) with the semiconductor integrated circuit formed therein are mounted on the semiconductor device surface. In such a semiconductor device, the bump electrodes are provided as the external terminals and the chip carrier substrate is provided to support the semiconductor elements thereon. For example, CSP (chip scale package), BGA (ball grid array), etc. are known as examples of this semiconductor device.
In recent years, with the demands of the small size, slim and lightweight structure of electronic devices, the surface mounting type semiconductor packages have come to be briskly adopted. Among the semiconductor packages of this type, the CSP is the general term of the semiconductor package having the small-size and slim structure, the size being equivalent to or slightly larger than the chip size.
For example, the CSP has been developed which is configured to have the structure that the semiconductor chips are carried on the surface of the chip carrier substrate, and a resin encapsulation portion is formed by carrying out the resin encapsulation to encompass the surface of the chip carrier substrate where the semiconductor chips are supported.
There are two kinds of the resin-encapsulation type semiconductor packages mentioned above: one using the tape substrate as the chip carrier substrate, and the other using the rigid substrate as the chip carrier substrate.
It is known that an example of the semiconductor packages of the kind using the tape substrate is the CSP in which a polyimide tape having certain flexibility is used as the tape substrate. On the other hand, it is known that an example of the semiconductor packages of the kind using the rigid substrate is the CSP in which a ceramic or resin substrate having certain rigidity is used as the rigid substrate.
The unified molding method has been developed as the technology of improving the efficiency of production of chip scale packages (CSP) which are manufactured using the rigid substrate or the tape substrate with low cost. In the unified molding method, two or more semiconductor elements (chips) are arranged in an array formation and mounted on the chip carrier substrate (for example, the rigid substrate), and the chip array region, including the semiconductor elements, is subjected to the resin encapsulation and molding in a unified manner so that the resin-encapsulation portion is formed. After the resin encapsulation is performed, the dicing is performed so that the chip array region with the resin-encapsulation portion formed is divided into the respective separate chips by cutting.
In recent years, there is the trend that the semiconductor packages using the rigid substrate are directed to having the inexpensive and slim structure, and such semiconductor packages are in the tendency that the rigid substrate is enlarged (or the whole substrate surface to be used to support the semiconductor element) and the rigid substrate has the slim structure.
Japanese Laid-Open Patent Application No. 2002-110718 discloses a manufacturing method of a semiconductor device. In this method, a plurality of semiconductor chips are supported on the tape substrate, and the unified resin encapsulation of the same is performed. It is disclosed that, in order to reduce the curvature of the resin encapsulation portion, the unified resin encapsulation is performed using the encapsulation mold which is provided with the convex portion on the cavity formation surface of the mold.
With the enlarged and slim structure of the rigid substrate, some small curvature and bending defects may arise in the chip carrier substrate of the semiconductor package due to the processing heat applied in the die-bonding process or the wire-bonding process.
Subsequently, the transfer molding process is performed. In the transfer molding process, the curvature or bending defects arising in the preceding process are pushed toward the vent-end of the mold (or in the direction where the resin flows) by the resin injection pressure, and the curvature or bending defects are concentrated on the vent-end of the mold. Hence, there is the problem that the rigid substrate will curve greatly.
Moreover, there is the problem that the semiconductor chips mounted on the rigid substrate are subjected to the residual stress due to the curvature or bending defects after the resin encapsulation is performed so that the semiconductor chips will be damaged, or the bonding wires will be deformed.
FIG. 1A and FIG. 1B are diagrams for explaining a conventional molding process of a semiconductor device using a rigid substrate.
FIG. 1A shows a state of the semiconductor device at the time of resin injection in the unified molding process of the semiconductor device, and FIG. 1B shows a state of the semiconductor device after the resin injection is performed.
The rigid substrate 1 of FIG. 1A is the circuit board which contains a printed circuit board made of glass epoxy resin or a ceramic substrate. It should be noted that the rigid substrate 1 has some rigidity unlike the tape substrate.
The electrodes and wiring pattern for interconnection with the electrodes of the semiconductor device are formed on the front surface of the rigid substrate 1, and the electrodes for interconnection with the external electrodes are formed on the back surface of the rigid substrate 1.
The encapsulation mold used by the molding process of FIG. 1A is provided with the upper mold 2 and the lower mold 3, and the mold cavity is formed on the back surface of the upper mold 2.
In the manufacturing method of the semiconductor device which is in the state before the resin injection as shown in FIG. 1A, the rigid substrate 1 is disposed between the upper mold 2 and the lower mold 3.
The die-bonding and wire-bonding processes are already performed with the rigid substrate 1 in the state of FIG. 1A, a plurality of semiconductor elements (chips) (not shown) are arranged in an array formation on the chip-support surface of the rigid substrate 1. The chips are mounted in the chip array region of the rigid substrate 1, and the electrodes (pads) of the semiconductor elements and the connection terminals (electrodes) of the rigid substrate 1 are connected each other by the bonding wires.
With the processing heat applied in the die-bonding process or the wire-bonding process, the curvature of the rigid substrate 1 may often arise.
As shown in FIG. 1A, the resin 11 is injected into the mold cavity of the upper mold 2 from the gate-end of the mold on the right-hand side of the figure.
As shown in FIG. 1B, the resin-encapsulation portion is formed by carrying out the resin encapsulation of the semiconductor elements (chips) carried on the chip support surface of the rigid substrate 1 collectively with the injected resin 11.
However, as described above, in the transfer molding process of FIG. 1A, the curvature or bending defects arising in the preceding process are pushed toward the vent-end of the mold (in the direction where the resin 11 flows) by the resin injection pressure, and the curvature or bending defects are concentrated on the vent-end of the mold. Therefore, there is the problem that the rigid substrate 1 will curve greatly.
In FIG. 1B, reference numeral 9 indicates the position of the rigid substrate 1 where a relatively large curvature of the rigid substrate 1 arises and the deformation of the wires connected to the semiconductor elements occurs.
On the other hand, in the semiconductor packages using the tape substrate, the tape substrate itself has some flexibility, and the problem of the wire deformation as shown in FIG. 1B does not arise. However, there is the problem that the tape substrate is expensive when compared with the rigid substrate, and it is not adequate to satisfy the recent requirements of the substrate enlargement and the cost reduction.